Fan for the ventilation of buildings,e.g.,stables



EU s. H. KIRISTIANSEN AWWW? FAN FOR THE] VENTILATION OF BUILDINGS, E.G., STABLES Filed Jan. 25, 1968 5 Sheets-Sheet 1 1970 s. H. KRISTIANSEN fiflwfifiii FAN FOR THE VENTILATION OF BUILDINGS, E.G., STABLES Filed Jan. 25, 1968 5 Sheets-Sheet 2 Jam. 6, 170 s. H. MRISTIANSEN FAN FOR THE VENTILATION OP BUILDINGS, E.G. STABLES Filed Jan. 25. 1968 5 Sheets-Sheet 5 WW 5. H. KRISTIANSEN ,4@7fi7 FAN FOR THE VENTILATION OF BUILDINGS, E.G. STABLES Filed Jan. 25. 1968 5 Sheets-Sheet 4 1970 s. H. KRISTIIANSEN $,%@?VV@W FAN FOR THE VENTILATION OF BUILDINGS, E.G., STABLES Filed Jan. 25, 1968 5 Sheets-$heet 5 United States Patent 3,487,767 FAN FOR THE VENTILATION OF BUILDINGS, E.G., STABLES Svend Helge Kristiansen, Naestved, Denmark, assignor to Nordisk Ventilator C0. A/S, Naestved, Denmark, a

company of Denmark Filed Jan 25, 1968, Ser. No. 700,549 Claims priority, application Denmark, Jan. 30, 1967, 533/67; May 24, 1967, 2,722/ 67 Int. Cl. F2415 7/06 US. CI. 98-33 6 Claims ABSTRACT OF THE DISCLOSURE A fan for the ventilation of buildings, e.g. stables, comprising two concentrical tubes in which two sets of interconnected concentric fan vanes are disposed so as to perform an injection of air through the outer tube and an exhaust of air through the inner tube, a by-pass being provided between the inner and the outer tube through a first damper which is coupled to a second damper in the outer tube and as the case may be also to one in the inner tube, in such a way that when the first damper is opened the other or others is or are closed and vice versa.

The invention relates to a fan for the ventilation of buildings, e.g. stables, in which the injection duct is fitted concentrically around the exhaust duct, in which exhaust duct the driving motor of the fan is fitted axially, which fan has two concentric, rigidly interconnected Sets of vanes of the type used in axial flow fans, which are arranged in such a manner that one set of vanes is located in one duct and the other set of vanes is located in the other duct and in which fan in the injection duct one or more adjustable dampers are provided.

On account of the particular characteristic curve of the axial flow fans, the throttling, performed for the control of the air volume, occasions that the fan has to operate within the so-called stalling range during a great part of its operational period. In this range the fan runs rather jerkily and noisily. In addition, the power consumption of the fan rises considerably when throttled.

The invention aims at providing a type of fan of the type discussed, by means of which the desired control of the injected quantity of air is achieved without the ment tioned drawbacks. 4

According to the invention. the injection duct is connected with the exhaust duct between the set of vanes and the dampers mentioned through an. adjustable damper, and the damping in the injection duct and in the connection between the two ducts are connected to each other and to a common adjustment means in'such a way that simultaneously with the opening of the damper in the injection duct, the damper between the two ducts is closed, and vice versa.

Through this, a by-pass is formed, which connects the pressure side of the set of vanes in the injection duct and the suction side of the set of vanes in the exhaust duct with each other, and by regulation of the damper in this by-pass in dependence of the adjustment of the dampers in the injection duct it is made possible to operate with very slight variations in the pressure in the injection duct in front of the dampers fitted therein. The air volume delivered by the fan is determined by this pressure and the resistance to the outflow, and thus is chiefly proportional to the passage cross section of the dampers, which, moreover, entails a more suitable control than is the case with the known fans of the kind discussed, in which the throttling occasions a rise in pressure, so' that no linear connection between the air volume delivered and the adjustment of the throttling means exists.

3,487,767 Patented Jan. 6, 1970 ICC In addition, by means of the measures stated, a saving in the power consumption is achieved, since the power consumption of the axial flow fan, as known, rises with increasing pressure and consequently decreasing air volume on account of which the power consumption rises with the known fans when the throttling increases while the pressure in the case of the fan according to the invention is maintained constant at a low value despite the injected air volume being throttled.

In an embodiment of the invention, a damper has also been provided in the exhaust duct, which is connected with said dampers and which respectively opens or closes simultaneously with the damper in the injection duct.

According to the invention it is advantageous that the total of the flow resistance through all the dampers is essentially constant irrespective of the adjustment of said dampers. It is thereby ensured that the fan operates constantly and essentially at the same point of its characteristic curve.

If this is employed in connection with a design of the fan in which the orifice or orifices of the injection duct runs or run in the main at right angles to the axis of the duct, it may be expedient, according to the invention, that the connection between the two ducts is formed by one or several apertures in the partition common between the two ducts, while the throttling means in this connection consists of a cylindrical piece of tubing, with a cross section corresponding to that of the common partition and which is displaceable in the axial direction in such a fashion that it can more or less cover the apertures, and that the throttling means for the orifices consist of a cylindrical piece of tubing, which adheres to the outer wall of the injection duct and is displaceable in the axial direction in such a manner that it is capable of more or less closing the orifices, in addition to which the two pieces of tubing are rigidly interconnected.

By this means a very simple construction of the coupled dampers is attained, and, in order to achieve the desired interrelation of the throttling means with the aid of the various dampers all that is required, is to appropriately dimension the aperture or apertures in the common partition between the two ducts.

Cited above, only the characteristic curve of the set of vanes in the injection duct has been taken into consideration. The characteristic curve of the set of vanes in the exhaust duct is of the same kind and plays a very important role in the dimensioning, since on account of the smaller diameter, the stalling range of the characteristic curve makes itself felt still more markedly. As to the regulating of the ventilation, it is sufiicient, to be in a position to throttle the injection apertures and the supply of an additional volume of air via the connection between the injection duct and the exhaust duct employed according to the invention, entails no difficulties.

On account of other reasons, however, it is expedient to be able to close the exhaust apertures, so that during the periods in which the fan is not in use a draught occurs, and, if in this case a design is employed in which also the orifice or orifices of the exhaust duct proceeds or proceed at right angles to its axis, it is according to the invention expedient that the piece of tubing adhering to the partition common to both ducts is extended to such a degree that it can close the exhaust duct and in such a way that it is closed completely when the connection between the two ducts is opened completely.

It a damper independent of the other dampers were to be employed in the exhaust duct, the risk might arise that the set of vanes fitted in this duct would operate in the stalling range. However. this is entirely prevented in the stated embodiment of the invention, since when the damper in the exhaust duct is closed gradually more and more, the connection between the two ducts is simultaneously being opened at the same rate, so that the inner set of vanes is being continuously supplied with that volume of air which suflicies to allow it to operate at the desired point of its characteristic curve.

Since the connection between the two ducts is generally located in the immediate proximity of both sets of vanes, if the dampers are arranged between the sets of vanes and the injection nozzle of the injection duct, it can at times be difiicult to achieve the desired control of the throttling of the connection between the two ducts. However, these ditficulties can, according to the invention, be removed to a large extent by the injection duct possessing a larger cross section in its part located behind the set of vanes than at the level of the set of vanes.

This is being achieved in a very simple manner, in an embodiment of the invention in which the annular member connecting the two sets of vanes, possesses U shape, the one branch of which lies at the same distance from the axis as the common partition of the two ducts and the other branch of which has a greater distance from the axis, while the piece connecting the branches is turned against the direction of the flow in the injection duct.

A particularly advantageous embodiment of the invention is characterized in that the adjustable damper between the injection duct and the exhaust duct is arranged between the cap, and the set of vanes.

When the aperture of the said damper is made larger or smaller a larger or smaller part of the air drawn off from the building is blown back into same and at the same time a regulation of the quantity of fresh air drawn in takes place in the opposite direction, so that the volume of air blown into the room to be ventilated from the fan remains essentially more or less the same, irrespective of how much or how little fresh air is to be fed to it. This entails that the flow pattern remains always substantially the same, independent of the adjustment, whereby it is considered easier to adjust the fan in order to prevent a draught under all conditions, than in the cases in which the volume of air blown into the room is varied from zero up to a maximum value, whereby the flow pattern is a different one for each of the various adjustments so that the adjustment, which has to be effected in order to prevent the occurrence of draught at all adjustments, can entail that the capacity of the fan is not being fully utilized.

Since it must be taken for granted that the fan is so dimensioned that it will satisfy the maximum ventilation requirement and that this requirement arises only on rare occasions when the weather is cool, the said damper is, as a rule, opened slightly and consequently the additional advantage is attained, that the drawn-cold fresh air mixes itself with the stale air from the room into which it is being blown back, and thus being already slightly warmed up in the fan prior to being blown into the room.

Moreover, the advantage is attained that the connection with the atmospheric air can be completely interrupted in those cases where no demand for fresh air exists, if one regards the ventilated room as a whole, yet the fan continues to effect the same circulation of the air so that the air in the room is in continual agitation and that the air from the various parts of the room is being mixed and thus more evenly distributed.

It can be particularly advantageous, according to the invention, that the dampers in both ducts and between same are each designed as one unit comprising two semicylindrical parts in which the diameter of the semi-cylindrical parts correspond to the diameter of the partition between both ducts and in which the semi-cylindrical parts are rotatable around an axis, which forms a diameter of both ducts as well as of these parts and which are so bevelled at the top that the bevels form the same angle to both sides of the plane separating the two semicylinders when the parts are in a position in which they are aligned essentially with the partition between the due s, a d a e ch of he two p rs, 9m 1 dg s wit which it abuts upon the other part in the said position, is provided with flanges that extend to the outside'and that the outer edges at these flanges and the lower edges of both parts are of such a shape, that in a position in which the beveled edges abut upon each other, their projection onto a normal plane in the ducts forms a circle, the radius of which is essentially equal to the outer radius of the injection duct.

By this means an extremely simple constructional solution of the in itself rather complicated problem is achieved to more or less block the passage through two concentric ducts and at the same time to open a connection between the two ducts through their cylindrical partition at the same rate.

Furthermore, it can be advantageous, according to the invention, to fit heating means in the injection duct between the set of vanes and the injection orifice. By means of this, the advantage which is due to the fact that the fresh air drawn in is being mixed with a greater or a lesser part of the exhausted, stale air in the fan itself, is increased still further, since by the employment of heating means an appropriate preheating of the injected air is ensured even in those cases, where the ventilation requirement is so great that the damper between the two ducts is either closed or only opened slightly.

It can, furthermore, be advantageous, according to the invention, to have cooling means fitted in the injection duct between the set of vanes and the injection orifice.

In particular, if heating means have already been provided at this point, with the aid of which, especially in stables, one is able to satisfy the heat supply requirement arising in connection with the ventilation, it is advantageous that cooling means do exist in the fan, so as to obviate the use of separate cooling means, and when the heating means happen to be heat exchangers through which a heating agent, e.g. warm water, is flowing, the same means can quite simply be utilized as cooling means, by having a cooling agent, e.g. cold water, flowing through same.

It is finally advantageous to have the orifice of the injection duct comprise 1015 nozzles, the axes of which lie on a level at right angles to the axis of the duct like the. radii of a circle which is concentric with the duct and that in each nozzle separately adjustable throttling means are provided. The optimum number of nozzles is 12, it. is, however, possible to reduce this number to 10, or to increase it to 15 without any deleterious effect. If the number is too low, the jets continue through the room as individual jets and have the effect of a draught. If the number is too high, the jets merge on account of the flow induction immediately below the nozzles so that they form a continuous, plate-shaped stream, which fully corresponds to an air current occurring in front of an annular passage slit, Such a plate-shaped air stream often tends to deflect downwards shortly after leaving the nozzles, so that currents are being created in the room which have the effect of a draught.

Qn the other hand, if the number of nozzles lies within the limits indicated, the individual jets will only merge at a certain distance from the nozzles, where the velocity of the flow has become sufficiently low, so that the deleterious, effects of the plate-shaped stream do not occur, but is stillv so high that the air flow does no longer continue through the room in the form of jets that are sharply defined against each other.

The invention will subsequently be explained in detail with reference to the drawing, which shows in FIG. 1 an embodiment of the invention in longitudinal section;

FIG. 2 a sectional view after the line II'II in FIG. 1;

FIG. 3 'a part of the fan shown in FIG. 1 with a different setting,

FIG. 4 the characteristic curve of an axial flow fan;

FIG. 5 a part of the fan shown in FIG. 1 with a modi; l design of a det il,

FIG. 6 a longitudinal section through a modified embodiment of the fan according to the invention;

FIG. 7 a sectional view after the line VIIVII in FIG. 6, however, with a changed setting of the fan;

FIG. 8 a section of the fan shown in FIG. 6, shown identically, but with modified setting and FIG. 9 a sectional view after the line IXIX in FIG. 8.

The fan shown in FIGS. 1, 2 and 3 has an impeller with two concentric sets of vanes 2 and 3 driven by a motor 1, in which impeller the vanes of the one set are, mounted on a hub 4 and are fastened at their outer extremities to an annular member 5, which carries the vanes of the set of vanes 3. The angle of pitch of these two sets differ by 180, so that the two sets blow in direction which are opposed to each other, and in the example shown in such a manner that the inner set of vanes blows in an upward direction and the outer set of vanes blows in a downward direction.

Coaxially with the vane sets 2 and 3 has been mounted partly a tube 6, which is in alignment with the member 5, and partly a tube 7, which surrounds the outer vane set 3. In this manner an exhaust duct 8 and an injection duct 9 are formed. The injection duct 9 is at its lower part provided with a number of orifices in the form of nozzles 10, the axes of which lie on a plane at right angles to the axis of the fan, while the exhaust duct 8 is covered at its lower end by means of a plate 11 at a certain distance from the termination 12 of duct 9, so that an annular intake aperture 13 is formed.

The partition 6 is interrupted from the impeller downwards up to the termination of the duct 9, and the aperture thus resulting between the ducts 8 and 9 is screened by a cylindrical piece of tubing 14, the diameter of which is substantially the same as that of the partition 6 between both ducts. This piece of tubing is carried by a number of spokes 15, which are fastened to an adjustment rod 16, which, with the aid of an adjustment motor 17, is displaceable in the axial direction, so that the piece of tubing 14 can be displaced and the connection between both ducts 8 and 9 can be more or less opened or closed. FIG. 3 shows the fan in a position, in which the ducts 8 and 9 are in unobstructed connection with each other via the aperture 18, which is adjusted to approximately half of its possible size.

A cylindrical piece of tubing 19 has been provided on the inside of the partition 7, which piece of tubing with the aid of a number of radial plates 20 is connected with the piece of tubing 14, and can be displaced together with tubing 14. The connection between the pieces of tubing 19 and 14 is of such a kind that, when the aperture 18 is enlarged from its completely closed position to its completely opened position, the piece of tubing is displaced, downwards in front of the nozzles 10, from a position in which the nozzles are fully open, to a position in which they are completely closed. Further the piece of tubing 14 is of such a length that it is able to slide, in the embodiment shown, downwards in front of the intake aperture 13, so that the throttling of this aperture on the whole corresponds to the throttling of the exhaust apertures.

The fan shown is mounted in the ceiling 21 of a building. The ducts 8 and 9 are carried through the roof 22 of the building and are screened above the roof by means of a cowling 23 and a screen 24. Since the design of both cowling and screen does not concern the invention, it is superfluous to describe them in detail, it should, however, be briefly mentioned that the design is of such a kind that an intake aperture 25 for the injection duct 9 and a discharge aperture 26 for the exhaust duct 8 is formed.

In the following the effect of the measures taken by means of the invention are to be described in detail based on the characteristic curves shown in FIG. 4. In this figure the curve shows the normal characteristic operating curve of an axial flow blower and the curve a shows the pressure as a function of the air volume. The curve b shows the power consumption of the drive motor as a function of the air volume.

The point P indicates the operational point at full performance.

If the connection between the ducts 8 and 9 in FIG. 1, indicated by the invention, does not exist, the regulation of the injected air volume can only be eflected by the throttling of the injection nozzles 10 and in such throttling the operating point of the fan moves on the curve a. It can be seen from the curve that in the case of such throttling that the air volume is reduced to half, the operating point of the fan is at a point P of the curve, which lies within the stalling range of the fan. At this point the fan runs unsteadily and very noisily. It can be seen from curve 12 that the power consumed by the drive motor thereby rises from the value N which corresponds to its maximum performance, to the value N If however, one employs, as specified by the invention, a connection between the two ducts 8 and 9 and regulates the aperture thereof in dependence of the throttling of the injection apertures, one can achieve that the pressure behind the blower is maintained approximately constant at the value corresponding to point P and that the air volume, which passes the blower vanes, corresponds to the value corresponding to this point. Despite this, the air volume injected is regulated in the desired manner, since it is on the whole proportional to the flow area determined by the damping means 19. By this means it is possible to adjust the fan in such a way that it operates at all times with maximum efliciency and at a steady point of the curve at a low noise level, and that the power consumed by the drive motor is being kept at a low value.

The inner vane set 2 operates according to a curve of the same characteristic as the one shown in FIG. 4. Even if throttling is used in the intake duct 13, as described in connection with FIGS. 1 and 3 above, so that the air volume drawn in is reduced the air volume is supplemented through the adjustment of the air volume flowing through the direct connection from duct 9 into duct 8. By appropriate dimensioning it can be achieved that the pressure below the interior fan blades 2 can be kept approximately constant, so that the fan operates at a certain extent at a constant point of the characteristic curve, resulting in the above-mentioned advantages.

At the same time it can be seen that more expedient progress of the throttling adjustment of the injection apertures 10 is being attained, since the air volume, as mentioned, varies linearily with the adjustment of the throttling means, as can be gathered from FIG. 4. This is not the case with known fans, which do not possess a connection between the ducts 8 and 9, in which the throttling not only entails a change in the flow section, but also a change in the pressure.

It can at times be diflicult to achieve a sufliciently safe control of the throttling in the connection between the two ducts 8 and 9, however, according to the invention it is shown that one can achieve a considerable improvement in this respect by the flow area of the injection duct at the level of the outer vane set 3 being smaller than in the part situated between impeller and injection apertures.

This can be expediently achieved by means of the embodiment shown in FIG. 5, which differs from the one shown in FIG. 1 in that instead of the cylindrical annular member 5, which interconnects the two sets, an annular member is employed, which, in radial section pOsseSses the form of a U. One branch 27 of this annular member possesses a cylindrical form and has the same diameter as the partition 6 between both ducts and is fastened to the extremities of the vanes 2, while the other branch 28, which proceeds parallel to the first, also forms a cylinder, which, however, has a greater radius and carries the vanes 3. The connection 29 between the two branches is turned against the flow direction in duct 9. It proves that by such a measure it is easier to adapt the adjustment of the throttling means 14 to the adjustment of the throttling means 19.

In a fan design like the one shown, the air is blown rather far away from the fan parallel to the ceiling of the building through nozzles in rather sharply defined jets. If such a jet strikes a wall or some other obstacle, it may be deflected in a detrimental direction so as to create a draught, however, this can be prevented by providing individually adjustable throttling means in each of the nozzles. This Way said throttling means may at the same time operate as guide vanes. By throttling the nozzles which are directed at a Wall or some other obstacle, it can be ensured that the length of the sharply defined jets is shortened by so much that such deleterious deflections cannot occur.

such a throttling will necessarily exercise a certain influence on the function of the fan since it is not accompanied by an adjustment of the connection between the ducts 8 and 9. Thus, a change in pressure takes place, which entails that the operating point of the fan on curve a in FIG. 1 is displaced. Since in practice such a throttling is to occur only in a few of the nozzles 10 which are present in a fairly large number, the shifting of the operating point is of only a very limited magnitude, so that it can under no circumstances bring the fan into the critical range and the automatic control with the aid of the throttling means 9 and 14 consequently continues to take place in precisely the same manner as described above, i.e. the new operating point lies essentially fixed on the curve, irrespective of the control.

The fan shown in FIGS. 6-9 comprises three parts, namely a cowling part 31, a control part 32 and a fan part 33, which are interconnected with the aid of pieces of tubing and 36 respectively, which lie between them and which are indicated by dotted lines. The fan is destined to be mounted in a building exactly like the one shown in FIGS. 1-5, and in such a manner that the cowling part 31 is situated above the roof of the building, while the fan part 33 extends partially through a ceiling in the building down into a room that is to be ventilated. The length of the pieces of tubing 35 and 36 is therefore adapted to the relative sizes of the building.

The fan part 33 comprises a motor 37, which drives an impeller with two concentric vane sets 38 and 39, of which one set is mounted on a hub 40. On the outer extremities of the vanes an annular member 41 is fixed, which carries the vanes of the vane set 39. The angle of pitch of the respective vanes of both sets differ 'by 180 so that both sets blow in directions which are opposed to each other and in the example shown in such a manner that the inner vane set blows in an upward direction and the outer vane set in a downward direction.

Coaxially with the vane sets 38 and 39 is mounted: a tube 42, which is in alignment with that part of the annular member 41 fixed to the outer extremities of the vanes of the vane set 38, and, a tube 43, which surrounds the outer vane set 39. Through this an exhaust duct 44 and an injection duct 45 are formed and these two coaxial ducts extend upwards through the piece of tubing 36, the control part 32, the piece of tubing 35, and up to the cowling part 31. The pieces of tubing 35 and 36 consequently comprise each two concentric tubes, as can be seen from the drawing. At its lower end the injection channel is provided with a number of orifices in the form of nozzles 46, the axes of which lie in a plane at right angles to the axis of the fan and are evenly distributed in such a manner that two each jointly form an angle of 30, i.e. the number of nozzles is 12. In the nozzles 46, heat exchangers 47 are mounted, which serve to heat or cool the air respectively with the aid of warm or cold water, as the case may be. Moreover, a guide vane set 48 is provided in each nozzle which can be adjusted independently of the guide vanes in the other nozzles which makes it possible to Control individually the air jets being discharged. Thus by controlling the direction of discharge of the nozzles, which have obstacles in the path thereof, detrimental deflections can be prevented without having to reduce the discharge flow areas of the other nozzles.

The control part 32 comprises one piece of tubing 48, which possesses the same diameter as the piece of tubing 43 and two pieces of tubing 49 which are concentric with the piece of tubing 48, the diameter of which corresponds to that of the piece of tubing 42. The pieces of tubing 49 are mounted at a certain distance from each other in the axial direction so as to create an aperture 50, through which the two ducts 44 and 45 are connected. The size of the aperture 50 can be controlled with the aid of a damper, which, in the embodiment shown is fitted in such a way that it simultaneously closes the passage through the ducts 44 and 45, so that both these ducts are completely blocked when the aperture 50 is opened to its maximum, but that they are completely opened when the aperture 50 is closed.

The said damper comprises two semi-cylindrical parts 51, the diameter of which corresponds to the diameter of the pieces of tubing 49. These semi-cylindrical parts 51 are pivoted on an axis, which lies in an axial plane of both semi-cylindrical parts 51 as well as of the pieces of tubing 49 and which are in a position at right angles to the axis of the pieces of tubing as well as to the axes of both parts 51. Moreover, the axis lies at an edge 52 of each of the parts 51 and these edges are cut ofl in accordance with a plane through the pivotal axis beveled in such a manner that the two edges 52 rest against each other when the parts 51 are turned into the position shown in FIG. 8.

The opposite edges 53 of the parts 51 are cut off according to a curve, which, in the position shown in FIG. 8 forms the line of intersection between the semi-cylindrical parts and the cylindrical partition 48.

Along their lateral edges 54, the semi-cylindrical parts 51 are provided with flanges 55 that extend to the outside in an axial plane.

When in the position shown in FIG. 8 the curve of intersection between the oblique cylindrical parts 51 and the cylindrical tube 48 is projected onto a plane that lies at right angles to the axis, it forms parts of a circle, which corresponds to a normal section of the tube 48. The outer edges 56 of the flanges 55 are shaped like segments of ellipses and in such a way that their projection onto the same plane forms the missing parts of the said circle. From this can be seen that the damper described in the position shown in FIG. 8 completely blocks the ducts 44 and 45 in an upward direction, i.e. in the direction towards the cowling part 31, while the aperture 50, which interconnects both ducts, is at its maximum passage.

When the parts 51 are turned into a position, in which their lateral edges 54 and 55 come to rest against each other they form a complete cylinder which fills the space of interruption between the pieces of tubing 49 in the control part, so that both ducts 44 and 45 are opened completely and that the aperture 50 between same is being closed completely.

The air volume passing through the vane sets 38 and 39 remains always approximately the same, irrespective of the position of the damper, which entails the advantage of the fan constantly operating at the most favourable point of its characteristic curve.

. Furthermore, essentially the same air circulation is achieved in the room to be ventilated, no matter how much or how little fresh air is being supplied, or none at all for that matter. Through this the air is distributed more evenly in the room, which provides the possibility of a better control and apart from this a better heat economy in those cases, where it is necessary, when the outside temperature is either too low or too high, to supply or draw off heat respectively with the aid of special heating or cooling agents, since a constant circulation of the air in the room has the effect that an especially high requirement of fresh air supply arising in certain places of the room is satisfied in part by the mixing with air from other parts of the room, so that for this reason less fresh air has to be supplied from outside.

The control of the damper comprising the parts 51 is carried out with the aid of rods 57, which are adjustable with the aid of a crank 58 fitted to a shaft 59. The adjustment can be carried out manually or automatically in dependence of the temperature and possibly the degree of humidity in the room, the means to be used for this purpose have, however, no bearing on the invention as such and need consequently not to be described in detail.

What is claimed:

1. An air injection and exhaust arrangement for the ventilation of buildings comprising: a fan, an exhaust duct, an injection duct fitted concentrically around the exhaust duct, a driving motor for the fan fitted axially within the exhaust duct, the fan having two concentric, rigidly interconnected set of vanes of the type used in axial flow fans, the vanes being so arranged that one set of vanes is located in one duct and the other set of vanes is located in the other duct, the exhaust duct being discontinuous over a portion of its length so as to interconnect the injection duct and the exhaust duct, damper means comprising two semi-cylindrical parts mounted in said disconnected portion of the exhaust duct so that in a first position the semi-cylindrical parts form a cylindrical section to close 06 said discontinuous portion and seal the exhaust duct with respect to said injection duct and, in a second position wherein said semi-cylindrical parts abuts one another to provide full communication between the injection duct and the exhaust duct at said discontinuous portion.

2. A device according to claim 1, wherein said injection duct terminates in an injection orifice at right angles to the axis of the ducts.

3. The device of claim 2, wherein heating and cooling means are mounted in the injection duct between the vanes and the orifice thereof.

4. The device of claim 3, wherein the injection orifice comprises a series of nozzles arranged in a common plane like radii of a circle.

5. A fan according to claim 1 characterized in that the orifice of the injection duct comprises some 10-15 nozzles, the axes of which lie on a plane, which is at right angles to the axis of the duct, like radii of a circle that is concentric with the duct, and that in each nozzle, damping means are provided which are separately adjustable.

6. An air injection and exhaust arrangement for the ventilation of buildings comprising: a fan, an exhaust duct, an injection duct fitted concentrically around the exhaust duct, a driving motor for the fan fitted axially within the exhaust duct, the fan having two concentric rigidly interconnected sets of vanes of the type used in axial flow fans, the vanes being so arranged that one set of vanes is located in one duct and the other set of vanes is located in the other duct, the exhaust duct being discontinuous over a portion of its length above the motor so as to interconnect the injection duct and the exhaust duct, damper means comprising two semicylindrical parts with flanges along the free longitudinal edges thereof, the parts having a diameter corresponding to the diameter of the exhaust duct and pivoted about an axis which is a diameter of both ducts and parts, the parts being bevelled at their upper edge so that when in a first position the parts form the cyindrical section to close off the discontinuous portion and seal the exhausted duct with respect to the injection duct, and in a second position wherein the bevelled upper edges of the parts sealingly abut one another and the flanges together with the lower edges of the parts engage and seal the injection duct, thereby sealing the exhaust and. injection ducts so that full communication between the ducts occurs at the discontinuous portion of the exhaust duct.

References Cited UNITED STATES PATENTS 1,487,828 3/1924 Ziganek et =11.- 98-33 2,595,370 5/1952 Rygard 9810 3,199,773 8/1965 Stirling 230-119 X 3,352,224 11/1967 Giilick 9810 3,401,621 9/1968 Aaberg 9833 WILLIAM E. WAYNER, Primary Examiner US. Cl. X.R. 230l14, 117 

